IR3522 International Rectifier, IR3522 Datasheet - Page 18

• Manufacturer Part Number: IR3522
• Description: DDR & VTT CONTROL IC
• Manufacturer: International Rectifier

IR3522
Serial VID Interface Protocol and VID-on-the-fly Transition
2
The IR3522 supports the SVI bus protocol which is based on Fast-mode I
C. SVID commands from a processor
are communicated through SVID bus pins SCL and SDA.
The SMBus send byte protocol is used by the IR3522 VID-on-the-fly transactions. The IR3522 will wait until it
detects a start bit which is defined as an SDA falling edge while SCL is high. A 7bit address code plus one write bit
(low) should then follow the start bit. This address code will be compared against an internal address table and the
IR3522 will reply with an acknowledge ACK bit if the address is one of the two stored addresses otherwise the ACK
bit will not be sent out. The SDA pin is pulled low by the IR3522 to generate the ACK bit. Table 1 has the list of
addresses recognized by the IR3522.
The processor should then transmit the 8-bit data word immediately following the ACK bit. The first bit is ignored
(bit 7). The IR3522 replies again with an ACK bit once the data is received. If the received data is not a VID-OFF
command, the IR3522 immediately changes the VREF1 analog outputs to the new target. VOUT1 and VOUT2 then
slew to the new VID voltages. See Figure 9 for a send byte example.
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Figure 9 Send Byte Example
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